1. n. [Drilling Fluids]
A unit of concentration, frequently abbreviated to ppm. For solid and liquid concentrations, ppm refers to weight (mass) units. For example: (1) Calcite in a ground barite sample may be 400 ppm. (2) Calcium chloride in a water solution may be 250,000 ppm. Note that the relationship of ppm to weight percentage is 10,000 ppm = 1 wt.%. For gases, ppm refers to volume (or mole) units. For example, H2S in an air sample may be 10 ppm (both by volume and by moles).